Establishing the Principles of Compositional Design for Long Life Rail Steels

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Railway track is a complex web of interconnected systems whose hub is the contact between wheel and rail. Consequently, degradation of rail is also a function of many system variables and the optimisation of the compositional design and microstructural attributes of this key component needs to be based on a thorough understanding and clear definition of the range of stress states experienced throughout a rail network. It is within this context that the proposed project is focused on the following tasks, the combined results of which will enable the optimisation of the compositional and microstructural design of rail steels to deliver the desired longevity and lower life cycle costs.1. Characterisation of metallurgical attributes: This will be undertaken on a wide range of rail steels both in the virgin and after controlled testing. Microstructural characterisation will include assessments such as measurement of interlamellar spacing, lath thickness, volume fraction cementite, and cementite dissolution.2. Establishing full range of wheel-rail contact conditions: The functionality required of the rail is highly dependent on the track and traffic characteristics and hence the wheel-rail contact conditions even within a single network can vary widely, from those for high-speed plain line to tight curves on mixed passenger and freight lines. Extensive past research results will be collated to define the range of contact conditions that could be encountered on a mixed traffic network3. Controlled laboratory tests: A large diameter twin disc test machine has been upgraded to enable development of a wide range of contact conditions that resemble those that are encountered in track. A novel methodology will be used to extract samples from commercially available rolled rails. These will be supplemented, if necessary, with rolled plates of bespoke compositions. Comparative resistance to wear and rolling contact fatigue will be established for the wide range of available and novel rail steels under closely controlled conditions.The results from the above analysis will be subjected to neural network analysis to establish the influence of the various compositional elements on the rate of degradation established under controlled testing. The expected output is a metallurgical design rule for the optimisation of rail steel compositions that could then form the basis for the rationalisation of compositions included in rail specifications, such as EN13674-1 2017.